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Cargo can be coerced to share credentials between registries

Low severity GitHub Reviewed Published May 25, 2026 in rust-lang/cargo • Updated Jun 26, 2026

Package

cargo cargo (Rust)

Affected versions

< 0.97.0

Patched versions

0.97.0

Description

The Rust Security Response Team was notified that Cargo incorrectly normalized the URLs of third-party registries using the sparse index protocol. If a hosting provider allowed multiple registries to be hosted with arbitrary names within the same domain, an attacker able to publish crates in a registry could obtain the credentials of others users of the same registry.

This vulnerability is tracked as CVE-2026-5222. The severity of the vulnerability is low, due to the extremely niche requirements needed to achieve the attack.

Overview

Originally Cargo only supported storing a registry's index within git repositories. Most git hosting solutions allow accessing a git repository with or without the .git suffix, so Cargo mirrored this behavior when normalizing registry URLs. This allowed credentials for https://example.com/index to be used for https://example.com/index.git.

This normalization was unintentionally applied to the new sparse indexes too. Sparse indexes can be hosted on any HTTPS server, which treat URLs ending with .git as different URLs than those without the suffix.

If the following conditions apply:

  • https://example.com/index is a sparse index.
  • https://example.com/index allows crates to depend on crates from any other registry.
  • The attacker is able to publish crates on https://example.com/index.
  • The attacker is able to upload arbitrary files to https://example.com/index.git.

...the attacker could configure https://example.com/index.git to be a Cargo sparse registry requiring authentication for downloads, and with a download URL pointing to a server recording any credentials set to it.

When the attacker then publishes a crate foo to https://example.com/index depending on a crate bar from https://example.com/index.git, and tricks the victim into downloading foo, Cargo will think the two registries share the same credential and send the victim's Cargo token to the malicious registry.

Mitigations

Rust 1.96, to be released on May 28th, 2026, will update Cargo to only strip the .git suffix from registry URLs using the git protocol. No mitigations are available for users of older versions of Cargo.

Affected versions

All versions of Cargo shipped between Rust 1.68 (the stabilization of sparse registries) and 1.96 are affected.

Acknowledgements

Cargo would like to thank Christos Papakonstantinou for reporting this issue according to the Rust security policy.

Cargo also wants to thank the members of the Rust project who helped address the vulnerability: Arlo Siemens for developing the fix; Weihang Lo, Eric Huss and Emily Albini for reviewing the fix; Emily Albini for writing this advisory; Emily Albini, Josh Stone and Manish Goregaokar for coordinating the disclosure.

References

@emilyalbini emilyalbini published to rust-lang/cargo May 25, 2026
Published by the National Vulnerability Database May 25, 2026
Published to the GitHub Advisory Database Jun 26, 2026
Reviewed Jun 26, 2026
Last updated Jun 26, 2026

Severity

Low

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements Present
Privileges Required None
User interaction Passive
Vulnerable System Impact Metrics
Confidentiality Low
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality Low
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(25th percentile)

Weaknesses

Use of Non-Canonical URL Paths for Authorization Decisions

The product defines policy namespaces and makes authorization decisions based on the assumption that a URL is canonical. This can allow a non-canonical URL to bypass the authorization. Learn more on MITRE.

CVE ID

CVE-2026-5222

GHSA ID

GHSA-p688-r7jv-fm6f

Source code

Credits

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